A polyacetal resin, which is an engineering plastic, is excellent in mechanical properties, electrical characteristics, sliding property, and chemical resistance, and thus, is widely used for, for example, automobile parts, electrical and electric equipment parts, OA parts, and the like. Among these, in particular, as use of the polyacetal resin utilizing excellent chemical resistance thereof, a flange, a valve, a tube, and the like which are connected to the fuel tank of an automobile, and parts for connecting a fuel tank that is in direct contact with fuel are exemplified.
On the other hand, in recent years, a polyethylene resin is used as a material for a fuel tank of an automobile for the purpose of improving fuel efficiency through weight saving of the body of the automobile.
Herein, as a method of installing parts for connecting a fuel tank made of the polyacetal resin to a fuel tank using a polyethylene resin, for example, a method of welding the polyacetal resin with the polyethylene resin, and the like are known. However, the method had problems such that the welding property of the interface between the polyacetal resin and the polyethylene resin is usually low, and the welding portion is easily separated by external force, and thus volatile fuel leaks out from the interface between the resins. Particularly, fuel has high volatility and can be a cause of air pollution, and thus such leakage of fuel is globally regulated. Accordingly, development of a polyacetal resin composition strongly adhering to a polyacetal resin and a polyethylene resin is strongly desired.
As an example of such a polyacetal resin composition, Patent Document 1 below discloses a resin composition obtained by blending a polyacetal resin and a polyethylene resin. Patent Document 1 below further discloses that a polyacetal resin has a proportion with respect to the total mass of the polyacetal resin and a polyethylene resin of 5 to 80 weight % and a melt flow rate of 0.1 to 200 g/10 minutes, and that as a polyethylene resin, a maleic anhydride-modified high density polyethylene having a maleic anhydride modification rate of 0.3% and a melt flow rate of 3.0 are used.